Method of photoetching at 180 to 220

ABSTRACT

Disclosed is a method of forming a pattern on a substrate, comprising a step of forming a light-sensitive layer containing an aromatic compound on a substrate, a step of patternwise exposing the light-sensitive layer with a light having a wavelength range shorter than the maximum wavelength; in the third absorption band from the long-wave side in the absorption spectrum of the aromatic compound and longer than the maximum wavelength in the fourth absorption band from the same, thereby to cause a photochemical reaction in the light-sensitive layer, and a step of developing the exposed light-sensitive layer, optionally after heat-treating the layer, so as to selectively remove the exposed area of the layer or leave the area as it is. The method gives a pattern having a high resolving power and an excellent dry-etching resistance.

This application is a Continuation application Ser. No. 08/181,413,filed on Jan. 14, 1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of forming patterns.

2. Description of the Related Art

In the field of electronic parts which need various fine workings, suchas semiconductor integrated circuits, fine working technology includingphotolithography is employed. The technology is carried out, forexample, in accordance with the following process.

First, a resist layer is formed on a semiconductor substrate, such assiliconwafer and the like, by a spin-coating method.

Next, the resist film is patternwise exposed to cause a photochemicalreaction thereon, developed and rinsed to form a desired resist pattern.

Further, using the resist pattern as an etching resistant mask, theexposed area of the substrate is etched to form fine lines and spaces(i.e. open area).

Recently, in order to attain large-scale integration with elevation ofthe density of electronic parts, it has been required to form fineresist patterns of submicron orders. As one means of satisfying therequest, a light source (ray source) of shortened wave length has beenemployed. For instance, a process of forming fine resist patterns byusing an ArF excimer laser (having a wavelength of 193 nm) or fifthharmonic wave of YAG laser (having a wavelength of 213 nm) has beendeveloped.

In the above-mentioned process, it is requested to form resist patternshaving an excellent dry-etching resistance for the purpose of moreeffectively carrying out fine working of the desired patterns. Regardingthe point, it is known that use of a light-sensitive compositioncontaining a compound having aromatic ring(s) or an aromatic compound asa resist material is effective. As such a resist material, for example,there are mentioned a resist composition containing an alkali-solublenovolak resin and a light sensitive agent of quinone diazide, which isused in the current mass-production process of producing LSI, and achemically amplifiable resist composition containing an alkali-solubleresin having phenolic nucleus/nuclei, a dissolution inhibitor and anoptical acid-generating agent, which is disclosed in Japanese Patentdisclosure No. 63-27829.

In conventional methods of forming patterns, exposure with theabove-mentioned short-wave ultraviolet rays and the like, using alight-sensitive composition containing an aromatic compound as a resistmaterial, for forming resist patterns having a high resolving power andan excellent dry-etching resistance has been attempted.

However, the above-mentioned resist material or a light-sensitivecomposition containing an aromatic compound especially has an extremelystrong absorption of light within a short wavelength range (about 190 nmor so) since the electrons of the aromatic ring in the compound areexcited with the light. Therefore, in the process of forming patternswhere the resist material (resist film) is exposed with a light sourcehaving the above-mentioned short-wave length lights, the material oftenhas over-absorption of the light during exposure. Therefore, thephotochemical reaction could not advance sufficiently through the resistfilm.

This phenomenon will be explained in more detail hereunder. It is knownthat the aromatic compound contained in the above-mentioned resistmaterial generally has three absorption bands to be caused by thestructure of the aromatic ring of the compound. Of them, the first andsecond absorption bands from the long-wave side are caused by theelectronic excitation as generated by molecular vibration, which shouldnot be generated from the intrinsic molecular symmetry, and thereforethey are not so strong. On the other hand, the third absorption band isextremely strong. In the conventional methods of forming patterns, sincethe exposure is effected with ultraviolet rays or the like having awavelength range near to the first and second absorption bands from thelong-wave side or having a wavelength range further longer than theseabsorption bands, the above-mentioned resist film does not have anystrong light absorption. However, where exposure with short-waveradiation rays or the like is employed, the above-mentioned resist filmwould probably have a strong light absorption due to the thirdabsorption band of the above-mentioned aromatic compound. In particular,where the above-mentioned resist film is exposed with an ArF excimerlaser the like, the light transmittance through the film is extremelysmall so that the intended photochemical reaction could not advancethroughout the whole film. As a result, a resist pattern having adesired resolving power and also having an excellent dry-etchingresistance could not be obtained, which is a problem.

The present invention has been made in view of the above-mentionedproblems.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of formingpatterns by short-wave exposure, which is applicable to photolithographyin a process of producing semiconductor devices and the like.

Another object of the present invention is to provide a method of stablyforming a pattern having a high resolving power and an excellentdry-etching resistance.

The above-mentioned objects of the present invention have been attainedby the following methods of forming patterns.

A method of forming a pattern on a substrate, comprising:

a step of depositing on the substrate a light-sensitive layer containingan aromatic compound including an aromatic ring with from 4 to 12conjugated double bonds;

a step of Patternwise-exposing the light-sensitive layer withelectromagnetic radiation having a wavelength range of approximatelyfrom 180 to 220 nm so as to cause a photochemical reaction in thelight-sensitive layer; and

a step of developing the exposed light-sensitive layer.

3. Detailed Description of the Preferred Embodiment

The method of the present invention comprises steps of depositing on thesubstrate a light-sensitive layer containing an aromatic compound havinga aromatic ring with from 4 to 12 conjugated double bonds;patternwise-exposing the light-sensitive layer with electromagneticradiation having a wavelength range of approximately from 180 to 220 nmso as to cause a photochemical reaction in the light-sensitive layer;and developing the exposed light-sensitive layer.

The "conjugated double bonds" as referred to herein means that pluraldouble bonds are connected with each other each via one single bond andare located on a plane. The aromatic ring of the kind is generallycyclized to be a 6-membered ring.

Considering in practice, the method of the present invention includesthe means for exposure and the constitution of the light-sensitivelayer, or the components of constituting the light-sensitive compositionto be used. In a method practiced in accordance with the presentinvention, an ultraviolet ray having a defined wavelength range(approximately from 180 to 220 nm) are used so as to obtain a patternhaving high resolving power. For example, an ArF excimer laser (193 nm)or a fifth harmonic of a YAG laser (213 nm)is employed as a light sourceand, according to this, a light-sensitive layer containing a compoundhaving aromatic ring(s) of a particular structure is used.

In general, if a structure has three or less conjugated double bonds,for example a benzene ring , the absorption region of the structure willbe near 180 to 220 nm. Accordingly, if a pattern is formed withultraviolet rays having the above-mentioned wavelength range, the lighttransmittance through the light-sensitive layer (resist layer) isdecreased when the layer includes benzene ring(s), so as to improve theetching resistance of the pattern. In that case, photochemical reactionby exposure the to rays could not sufficiently advance throughout thewhole thickness of the layer.

According to a method practiced in accordance with the presentinvention, an aromatic compound with four or more conjugated doublebonds is used so as to shift the absorption band of the compound to alonger-wavelength. Therefore, an absorption by the compound inwavelength range of 180 to 220 nm will be reduced. As a result, thelight transmittance through the light-sensitive layer during exposure iselevated and the photochemical reaction thereby advances sufficientlythroughout the whole layer in its thickness direction. Finally both ahigh resolution and an excellent dry-etching resistance can be achievedby the characteristics of the aromatic compounds.

In the method as mentioned above, the structure of the aromatic ring(s)in the aromatic compound contained in the light-sensitive layer issuitably selected in accordance with the ultraviolet rays with a definedwavelength range for exposure. That is, an overlap of the respectivewavelength ranges of the exposure rays and the absorption band of thearomatic compound contained in the light-sensitive layer should beavoided in order to improve the light transmittance through thelight-sensitive layer and obtain an intended fine pattern.

Next, the above-mentioned method is explained in detail in order of thesuccessive steps.

In the first step, a solution (varnish) of a light-sensitive compositioncontaining, an aromatic compound having an aromatic ring with from 4 to12 conjugated double bonds in the structure, is coated on a substrate,for example, by using a spin coating method or a dip coating method.Then it is dried at a temperature of approximately from 60° C. to 150°C., preferably approximately from 80° C. to 130° C., to alight-sensitive layer (resist film).

As the substrate, for example, usable are a silicon wafer, a siliconwafer having thereon various insulating films, electrodes or electricwires, a blank mask, a semiconductor wafer of III-V compounds such asGaAs, and the like.

On the other hand, the above-mentioned light-sensitive composition isresist material, including at least one aromatic compound having aaromatic ring with from 4 to 12 conjugated double bonds as a maincomponent or other component of the resist material.

The aromatic compound having aromatic ring(s) with from 4 to 12conjugated double bonds used in practicing the method of the presentinvention are compounds of which the particular aromatic ring(s) can bebeen introduced into the molecular skeletons, for example, into the mainchain skeleton and/or side chain skeleton. Examples of a light-sensitivecomposition include positive resist containing a compound having a mainchain of which is cut by exposure,or compound whose solubility iselevated by exposure; and negative resist containing containing compoundhaving a main chain of which is cut by exposure, or compound whosesolubility is lowered by exposure. Of them, useful is a chemicallyamplifiable resist in which the photochemical reaction is amplified bythermal reaction after the exposure thereto.

The above-mentioned aromatic ring with from 4 to 12 conjugated doublebonds is, for example, a ring having a skeleton of a benzene ring, apyridine ring or the like in which one or more atoms of bonding to theskeleton ring are bonded to other atom(s) via double bond(s). Specificexamples of the ring include benzene ring skeletons, pyridine ringskeletons or the like as substituted by unit(s) of ##STR1## (where R₁and R₂ each represents a mono-substituted carbon atom or nitrogen atom;R₃ represents a carbon atom; and R₄ represents oxygen atom or amono-substituted nitrogen atom or a di-substituted carbon atom).

The above-mentioned aromatic rings may also be condensed rings (i.e.,heterocyclic rings) composed of the above-mentioned benzene ring,pyridine ring and other mono-cyclic rings, as they have an excellentplane property. Examples of the heterocyclic rings include pyrrole,benzofuran, benzothiophene, indole, benzoxazole, benzothiazole,indazole, chromene, quinoline, cinnoline, phthalazine, quinazoline,dibenzofuran, carbazole, acridine, phenanthoridine, phenanthroline,phenazine, thianthrene, indolidine, naphthyridine, purine, puteridine,fluorene, benzoquinone, phthalimide, phthalic acid anhydride skeletonand the like.

The above-mentioned aromatic ring having from 4 to 12 conjugated doublebonds is preferably a condensed ring composed of 6-membered rings, sincethe pattern to be formed may have an extremely improved dry-etchingresistance. Examples of the condensed ring include naphthalene,anthracene, phenanthrene, pyrene, naphthacene, chrysene,3,4-benzophenanthrene, perylene, pentacene and picene. In addition,biphenylene and biphenyl are also preferred structures, as they give anexcellent dry-etching resistance. In particular, where the aromatic ringis selected from naphthalene, anthracene and phenanthrene, thetransparency and dry-etching resistance of the pattern to be formed arefinally elevated.

In the above-mentioned method, it is preferred that the proportion ofthe aromatic rings having from 4 to 12 conjugated double bonds is about60% by weight or more of all the aromatic rings in the light-sensitivecomposition. The reason is because if it is less than about 60% byweight, the light transmittance of the light-sensitive layer isdeteriorated. The proportion is more preferably within the range ofabout from 75 to 100% by weight. The proportion of the above-mentionedparticular aromatic compound in the solid content of the light-sensitivecomposition is preferably from 10% by weight to less than 90% by weight.The reason is because if the content of the aromatic compound is lessthan 10% by weight, the dry-etching resistance of the pattern to beformed is decreased, but if it is 90% by weight or more, the lighttransmittance of the light-sensitive layer is decreased. The content ofthe aromatic compound is more preferably from about 20 to 50% by weight.

Where the above-mentioned aromatic ring is substituted by hydroxylgroup(s) or protected hydroxyl group(s) such as OR₅ (where R₅ representstert-butyl group or tert-butoxycarbonyl group), the compound containingthe ring may be finally soluble in alkali substances after exposurethereto. Therefore, the compound is extremely suitable in thepattern-forming process using an alkali substance for development.

The light-sensitive composition (resist) including an aromatic compoundhaving the above-mentioned particular aromatic ring(s) is desired tohave a melting point of approximately 50° C. or higher, and it isdesired to have a high solubility in coating solvents in view of thecoatability thereof.

In the positive resists, negative resists and chemically amplifiableresists, aromatic ring(s) with from 4 to 12 conjugated double bonds havebeen introduced into the skeletons, which is for example, the skeletonof the main chain and/or side chain of the resin components, or theoptical acid-generating agents and dissolution inhibitors.

Specific examples of the positive resist include a resin compositionincluding a homopolymer or a copolymer of a vinyl or acrylic compoundhaving aromatic ring(s) with 4 to 12 conjugated double bonds such asnaphthalene ring, anthracene ring and the like in the side chain(s) andan acrylic compound such as methyl methacrylate, α-chloromethacr ylate,trifluoroethyl α-chloroacrylate, trifluoromethyl acrylate, and the like;a resin composition including a light-sensitive compound such aspolysilane having aromatic ring(s) such as naphthalene ring in the sidechain(s); and a phenolic resin including a naphthoquinone diazidecompound having aromatic ring(s) such as naphthalene ring and the like.

Specific examples of the negative resist include a copolymer of a vinylor acrylic compound having aromatic ring(s) such as naphthalene ring,anthracene ring and the like in the side chain(s) and conventionalpolymerizable compounds, such as an acryl methacrylate, a methacrylatehaving epoxy group(s) in the side chain(s), maleic anhydride, sulferdioxide (SO₂) l or an acrylic compound where the number of the carbonatoms in the ester side chain(s) is 4 or more: a resin compositionincluding a light-sensitive compound such as polysiloxane havingaromatic ring(s) such as naphthalene ring in the side chain(s); and acomposition comprising a phenolic resin having aromatic ring(s), such asnaphthol, and a photo-crosslinking agent.

The compositions may optionally include a sensitizing agent such as abisazide compound or the like, if desired.

As specific examples of the above-mentioned chemically amplifiableresist, the following compounds are mentioned. The chemicallyamplifiable resist includes a compound capable of generating an acid oran alkali by exposure, (i.e., an optical acid-generating agent, opticalalkali generating agent) and a compound having at least one bond capableof being decomposed by an acid or alkali.

Examples of a chemically amplifiable positive resist, include a resincomposition including a resin component comprising a copolymer of avinyl or acrylic compound having aromatic ring(s) with 4 to 12conjugated double bonds in the side chain(s) and a compound havingtert-butyl ester(s) such as tert-butyl methacrylate ortert-butoxycarbonyloxyvinylnaphthalene in the side chain(s) or anacrylic or vinyl compound having tert-butyl ester(s) in the sidechain(s), and an optical acid-generating agent and optionally a compoundhaving at least one bond capable of being decomposed by an acid (i.e.,dissolution inhibitor). If the composition includes the dissolutioninhibitor, the resin component will not need to include a tert-butylester, although they may used as a mixture. In that case, the resin maybe a copolymer including as a component a vinyl compound having analkali-soluble group such as methacrylic acid or the like which givesalkali-solubility to the copolymer.

Specific examples of the above-mentioned optical acid-generating agentinclude compounds such as sulfonyl compounds, sulfonate compounds,4-quinone-diazide compounds, onium salts such as sulfonium salts,iodonium salts and the like.

Specific examples of the above-mentioned dissolution inhibitor includetert-butoxycarbonyl compounds, tert-butyl ester compounds, pyranyl ethercompounds, trimethylsilyl protected OH or COOH compounds and the like.The optical acid-generating agent and the dissolution inhibitor may alsohave in the structure an aromatic ring with 4 to 12 conjugated doublebonds such as naphthalene ring or an anthracene ring in the structure,in accordance with the amount thereof to be in the resin composition.

The amounts of the individual components which comprise theabove-mentioned positive chemically amplifiable resist are defined asfollows: The amount of the acid generating agent contained in the resistis, though varying depending upon the strength of the acid to begenerated therefrom, generally defined to fall within the range ofapproximately from 0.5 to 30% by weight. If it oversteps the range, thesensitivity of the resist is decreased or the resolving power thereof isdecreased. The amount of the dissolution inhibitor contained in the sameis generally defined to fall within the range of approximately from 5 to99% by weight. If it oversteps the range, the sensitivity of the resistis also decreased or the resolving power thereof is decreased, like theabove.

On the other hand, examples of a chemically amplifiable negative resistinclude a resin composition including a a copolymer of a vinyl oracrylic compound having aromatic ring(s) with 4 to 12 conjugated doublebonds in the side chain(s) and an alkali-soluble acrylic or vinylcompound such as acrylic acid, vinyl naphthol or the like, an opticalacid generating agent, and a compound capable of crosslinking thepolymer with an acid or an optical crosslinking agent.

Specific examples of the above-mentioned optical acid-generating agentinclude halogenated alkyl-substituted triazine and naphthyridinecompounds, in addition to the compounds previously mentioned for thepositive resist. Examples of the above-mentioned optical crosslinkingagent include vinyl or acrylic copolymers having epoxy group(s) in theside chain(s) and also melamine compounds such as methylol-substitutedN-containing heterocyclic compounds, such as triazine or naphthyridineand so on.

The amounts of the individual components which comprise theabove-mentioned chemically amplifiable negative resist are defined asfollows: The amount of the acid generating agent contained in the resistis, though varying depending upon the strength of the acid to begenerated therefrom, generally defined to fall within the range ofapproximately from 0.5 to 30% by weight. The amount of the opticalcrosslinking agent contained in the same is preferably defined to fallwithin the range of approximately from 0.5% to 40% by weight. If theyoverstep the ranges, the sensitivity of the resist is decreased or theresolving power thereof is decreased.

The above-mentioned light-sensitive composition may optionally include asurfactant as a film improving agent or a dye as a reflection inhibitor.

The light-sensitive composition may be prepared by dissolving theabove-mentioned components and other additives in a suitable solventfollowed by filtering the resulting solution. Examples of solventsusable for the dissolution include, for example, water ketone solventssuch as cyclohexanone, acetone, methyl ethyl ketone, methyl isobutylketone and the like; cellosolve solvents such as methyl cellosolve,methyl cellosolve acetate, ethyl cellosolve, ethyl cellosolve acetate,butyl cellosolve, butyl cellosolve acetate and the like; ester solventssuch as ethyl acetate, butyl acetate, isoamyl acetate, ethyl lactate,methyl lactate and the like; alcohol solvents such as 2-butanol, isoamylalcohol, diethylene glycol and the like; polyalcohol derivative solventssuch as ethylene glycol diethyl ether, diethylene glycol monoethylether, ethyl carbitol and the like; and morpholine,N-methyl-2-pyrrolidone. These solvents may be used either singly or as amixture of them.

A preferable example of the above mentioned light-sensitive composition(resist) including at least one aromatic compound having an aromaticring with from 4 to 12 conjugated double bonds in the structure is alight-sensitive composition(A) shown below.

The light-sensitive composition(A) comprises:

(a)acetal resin having a unit represented by a following formula(1), andat least one unit selected from units represented by a followingformulas (2), (3) and (4): ##STR2## (wherein R₆ represents alkyl group,R₇ represents carboxylic group or alkyl group having an amino group, R₈represents an aromatic group, l, m, n 0, 1+m+n>0, x>0)

(b) epoxy resin including in the skeleton naphthalene ring, and

(c) compound capable of generating an acid or alkali by exposure.

The light-sensitive composition(A) include acetal resin. Theabove-mentioned acetal resin in the light-sensitive composition(A) canbe obtained by the acid catalyzed reaction of polyvinylalcohol withaldehyde containing R₆ -R₈ substituent.

In the above-mentioned method a unit represented by following formula(5)remained as small amounts of unreactant units of polymer precursor ofpolyvinyl acetate, which is a starting material of polyvinylalcohol.##STR3## (wherein y>0)

The molecular weight of the above mentioned acetal resin is preferablyin a range of 1,000 to 300,000. If the molecular weight of theabove-mentioned acetal resin is out of the above-mentioned range, asolubility of the acetal resin to the solvent is decreased.

A content of unit represented by formula(1) in the acetal resin ispreferably arbitrarily selected in accordance with a solvent in whichthe the acetal resin is dissolved. If the acetal resin is dissolved inthe water or alcohol-series solvent, a content of unit represented byformula(1) is preferably 50 mol % or less. If the acetal resin isdissolved in an organic solvent except alcohol, content of the unitsrepresented by formula(2) is preferably 50 mol % or more. If the contentof unit represented by formula(1) is out of these range, a solubility ofthe acetal resin to the corresponding solvent is decreased.

A content of unit represented by formula(3), or (4) is preferably 50 mol% or less for synthesys reason. If the content of unit represented byformula(3) or (4) is out of these range, the starting resin iscross-linked in a synthesis process. Therefore, corresponding the acetalresin can not be obtained.

The unit represented by formula(3) gives effects of increasing ansolubility of the resin to acid, and the unit represented by formula(4)has effects of increasing a solubility to alkali, each of them arepreferably introduced at least 1 mol %, more preferably, 5 mol %-30 mol%.

The light-sensitive composition(A) include an epoxy resin containingnaphthalene ring in the skeleton. By including the epoxy compoundcontaining naphthalene ring in the skeleton, a photosensitivity of thelight-sensitive composition(A) is improved.

All of the naphthalene compounds having at least one, and preferably 2or more epoxy groups in a molecule can be employed, preferably epoxyresin or epoxy compound which are synthesized by the reaction ofpolyhydroxynaphthalene with epichlohydrine in the presence of basiccatalyst.

Example of the polyhydroxynaphthalene compound are preferablynaphthol-series compound such asdihydroxidenaphthalene, naphthol-novolakcompound which is obtained by condensing naphthol-series compound byformaldehyde.

The content of the epoxy compound containing naphthalene ring, ispreferably arbitrarily selected in accordance with a molecular weight ofthe epoxy compound containing naphthalene ring, 1-70 parts by weight,preferably 5-50 parts by weight. If the content of the epoxy compound isless than one part by weight, the composition does not have sufficientphoto sensitivity. On the other hand, if the content of the epoxycompound is more than 70 parts by weight, the composition does not havesufficient heat resistance and transparency, and uniform coatings cannot be obtained with conventional spin-coating method,which is usuallyemployed in the resist process on semiconductor substrates.

Example of the compound capable of generating an acid by exposure (i.e.optical acid generating agent) in the light-sensitive composition(A),are onium salts, derivatives of oquinone diazide sulfonate, sulfonylcompounds, sulfonic acid esters, organic halogen compounds and the like.Example of the onium salt are: diazonium salts, phosphonium salts,sulfonium salts, iodonium salts, each having PF₆ ⁻, SbF₆ ⁻, AsbF₆ ⁻, CF₃SO₃ ⁻ (trifluoromethanesulfonic anion), CH₃ C₆ H₄ SO₃ ⁻ (p-toluenesulfonate anion), or like which functions as a counter anion. Onium saltof Trifluoromethanesulfonic acid andtriarylsulfide are more suitable foruse in the invention. These onium salts are known as optical acidgenerating agent which are very sensitive to a chemical radiation.Example of the sulfonyl compounds are: discrived in Japanese patentapplication No. H4-53729, Example of sulfonyl compounds are derivativesof arylmethyl sulfone, derivatives of bis(arylsulfonyl)methane,derivatives of diaryl methylsulfonylmethane, derivatives ofdimethylsulfonylmethane and, derivatives of α,α-bis(arylsulfinyl)diazomethanes, and the like, for example,bis(phenylsulfonyl)methane, (phenylsulfonyl)acetonitrile,1-methyl-2((phenylsulfonyl)methyl)benzene and the like have so highphoto-sensitively that they are especially suitable for use.

The organic halogen compounds, described above, are compounds which firmhydrohalogenic acid. Examples of these compounds are those disclosed inU.S. Pat. No. 3,515,552, U.S. Pat. No. 3,779,778, and Germanoffenlegungsschrift 22 43 621.

Example of other compounds which generate acids when exposed to chemicalradiations are those disclosed in Published Unexamined Japanese PatentApplications 54-74728, 55-24113, 55-77742, 60-3626, 60-138539, 56-17345,and 50-36209.

More specifically, examples of the compounds which generate acids whenexposed to chemical radiations are: di(p-tert-butylbenzene)diphenyliodoniumu trifluoro-methanesulfonate, benzoine tosylate,o-nityobenzyl p-toluenesulfonate, triphenylsulfoniumtrifluoromethane-sulfonate, tri(tert-butylphenyl)sulfoniumtrifluoromethanesulfonate, benzenediazoniumu p-toluenesulfonate, 4-(din-propylamino)-benzoniumtetrafluoroborate,4-p-tolyl-mercapto-2,5-diethoxy-benzeneduazonium hexafluorophosphate,tetrafluoro borate, diphenylamine-4-diazobium sulfate, 1,8-naphthalimidyl triflate, nafthalene containing onium salts(NAT-103,NAT-105, NDS-103, NDS-105 acid generator (Midori-Co., CAS 131582-00-8!,137867-61-9! and 110098-97-0!)), 4-methyl-6-trichloromethyl-2-pyrrone,4-(3,4,5-trimethoxy-styryl)-6-trichloromethyl-2-pyrone,4-(4-methoxy-styryl)-6-(3,3,3-trychloro-propenyl)-2-pyrone,2-trichloromethylbenzimidazole, 2-tribromomethyl-quinolone,2,4-dimethyl-1-tribromoacetyl juinolone,2,4-dimethyl-l-trybromoacetyl-benzene, 4-dibromoacetyl-benzoic acid,1,4-bis-dibromomethylbenzene, tris-dibromomethyl-S-triazine,2-(6-methoxy-naphthyl-2-yl)-4,6-bis-trichloromethyl-S-triazine,2-(naphthyl-1-yl)-4,6-bis-trichloromethyl-S-triazine,2-(naphthyl-2-yl)-4,6-bis-trichloromethyl-S-triazine,2-(4-ethoxyethyl-naphthyl-1-yl)-4,6-bis-trichloromethyl-S-triazine,2-(benzopyranyl-3-yl)-4,6-bis-trichloromethyl-S-triazine,2-(4-methoxy-anthoracyl-1-yl)-4,6-bis-trichloromethyl-S-triazine,2-(phenantyl-9-yl)-4,6-bis-trichloromethyl-S-triazine,o-naphthoquinonediazide-4-sulfonic chloride, and the like.

In the case of the light-sensitive composition(A), the content of theacid generating agent when exposed to a chemical radiation(i.e., theacid generating agent) is 0.01% to 20% by weight, preferably 0.2% to 10%by weight based on the weight of the solid components of thecomposition.

If the content of the acid-generating agent is less than 0.01% byweight, it does not efficiently work as a catalyst in the decompositionreaction or the crosslinking reaction. If the content of theacid-genereating agent is more than 20% by weight, it may result theuniform resist film.

Example of the compound capable of generating an alkali by exposure i.e,alkali generating agent in the light-sensitive composition(A), arecarbamate compound, sulfonamide compound, especially nitrobenzilcyclohexylcarbamate, dimethoxybenzylcyclohexylcarbamate,N-Cyclohexylmethylphenylsulfonamide, N-cycrohexyl-naphthylsulfonamideare more suitable for use in the invention. In the case of thelight-sensitive composition(A), the content of the optical alkaligenerating agent is 0.01% to 20% by weight, preferably 0.2% to 10% byweight based on the weight of the solid components of the composition.

If the content of the optical alkali-generating compound is less than0.01% by weight, it does not efficiently work as catalyst in thedecomposition reaction or or crosslinking compound. If the content ofthe optical alkali generating agent is more than 20% by weight, it maymake also result the uniform resist coating.

The light-sensitive composition(A) is one of the most preferablecomposition. This is because of a high efficiently of the cross-linkingreaction by the photo-irradiation, and the enough transparency duringthe exposure. In the acetal resin, photo-acid or photo-alkali catalyzedreactions make the layer (film) insoluble of the intermolecularcross-linking and and the simulataneous elimination of hydroxyl group.These mechanism are effectively applied to the negative resist.

And by adding a epoxy compound to above-mentioned light-sensitivecomposition including the acetal resin, a crosslinking efficiency andphotosensitivity are increased. The introduction of the naphthalene ringinto the skeleton of the epoxy compound is also preferable, since itraises the total content of carbon in the composition, therefore it alsoraises the dry etching resistance of the resist layer.

Another preferable example of the light-sensitive composition containingat least one aromatic compound having an aromatic ring with from 4 to 12conjugated double bonds in the structure is a light-sensitivecomposition(B) shown below.

The light-sensitive composition(B) comprises:

a copolymer of vinyl compounds having an epoxy group in the side chain;

a polyhydroxide compound having naphthalene ring in the skeleton; and

a compound capable of generating an acid or alkali by exposure.

Example of the copolymer of vinyl compound having an epoxy group in theside chain is a copolymer of glycidyl methacrylate, a copolymer ofalyciclyl ether, a copolymer of 1,2-epoxy-5,9-cyclododecadiene, acopolymer of 1,2-epoxy-5-hexene, or a copolymer of methylvinyloxirane.

Preferably, the copolymer of vinyl compound having epoxy group in theside chain, is the 3 components copolymer of vinyl compound having epoxygroup in the side chain, vinyl compound having aromatic ring in the sidechain and vinyl compound having carboxyl group in the side chain. Thelight sensitive compound(B) containing the copolymer described above hassufficient photosensitivity and sufficient alkali solubility and highdry etching resistance.

Examples of above mentioned vinyl compound having an aromatic ring inthe side chain are styrene, vinylnaphthalene, vinyl anthracene, vinylcarbazol, vinyl phenol, vinyl naphthol and chloro methyl styrene.

Example of above mentioned vinyl compound having carboxylic acid in theside chain are acrylic acid, methacrylic acid and maleic anhydride.

The copolymers with these acidic groups may also be formed with thede-protection reaction of the corresponding copolymers of trimetylsirilester or tert-butyl ester of acid substituted vinyl compounds.

The said 3 components copolymer preferably including 5-40 mol % of vinylunit having epoxy group in the side chain, 10-60 mol % of vinyl unithaving aromatic ring in the side chain and 10-50 mol % of vinyl unithaving carboxylic group in the side chain. If the contents of each vinylunits having epoxy group fall in said range, one of photosensitivity andsufficient alkali solubility and dry etching resistance of lightsensitive composition are decreased.

The light-sensitive composition(B) includes the polyhydroxide compoundas a cross-linking agent. Examples of polyhydroxide compound can bepreferably naphthol-series compounds such as dihydroxynaphthalene, andnaphthol novolak compound which is obtained by condensingnaphthol-series compound by aldehydes.

The content of the polyhydroxynaphtalene compound is preferablyarbitrarily selected in accordance with a content of epoxy group beingcontained in other solid components of the composition. The preferablecontent of polyhydroxide compounds is 1-50 parts by mole fractions ofepoxy group in the solid components of the composition, more preferably5-50 parts by mole fractions of epoxy group in the solid components ofcomposition. If the content of the polyhydroxidenaphthalene compound isless than 1 part by mole fraction of epoxy group in the solid componentsof composition, dry etching resistance of the light sensitivecomposition will be decreased. If the content of thepolyhydroxidenaphthalene compound is more than 50 parts by mole fractionof epoxy group in the solid components of composition, the coatingcharacteristics and/or solubility to the resist solvent are gettingworse.

Example of the optical acid generating agent by exposure in thelight-sensitive compound(B), and the optical alkali generating agent areexemplified for above-mentioned for light sensitive composition(A). Inthe case of the light-sensitive composition(B), the content of theoptical acid or alkali generating agent may be 0.01 to 20% by weight,preferably 0.2 to 10% by weight based on the weight of the solidcomponents of the composition.

If the content of the acid or optical alkali-generating agent is lessthan 0.01% by weight, the sensitivity of the light sensitive compositionwill decreased. If the content of the optical acid or alkali generatingcompound is more than 20% by weight, the coating characteristics will beworse.

In the case of the light sensitive composition(B), the copolymer ofvinyl compound having epoxy group effectively cross-links by ancatalysis of the optical acid or alkali generating agent.

The above-mentioned light sensitive composition(A) and (B) mayoptionally include a surfactant as a film improving agent or dye as areflection inhibitor.

The light sensitive-composition(A) and (B) may be prepared by dissolvingthe above-mentioned components and other additives in a suitable solventfollowed by filtering the resulting solution. Examples of solventsusable for the dissolution include, for example water, ketone solventssuch as cyclohexanone, acetone, methyl ethyl keton, methyl isobutylketone and the like; cellosolve solvents such as methyl cellosolve,methyl cellsolve acetate, ethyl cellosolve, ethyl cellsolve acetate,butyl cellosolve, butyl cellosolve acetate, and the like; ester solventssuch as ethyl acetate, butyl acetate, isoamyl acetate, ethyl lacetate,methyl lactate and the like; alcohol solvents such as 2-butanol, isoamylalcohol, diethylene glycol and the like; polyalcohol derivative solventssuch as ethylene glycol diethy ether, diethylene glycol monoethyl ether,ethyl carbitol and the like; and monopholine, N-methyl-2-pyrrolidone.These solvents may be used either singly or as a mixture of them.

Next, in the second step to follow the above-mentioned first step, thelight-sensitive layer is patternwise-exposed with a electromagneticradiation light having a wavelength range from 180 to 220 nm to cause aphotochemical reaction in the light-sensitive layer. As a light source,for example an ArF excimer laser (193 nm) or fifth harmonics of YAGlaser (213 nm) is employed. As a concrete operation for the exposure,the light-sensitive layer is patternwise-exposed to the light via a maskhaving a desired pattern.

In this step, the light-sensitive layer contains as an essentialcomponent, an aromatic compound having an aromatic ring with from 4 to12 conjugated double bonds in the structure, so that the lightabsorption in the exposed area of the light-sensitive layer is reducedand the light transmittance through the area is extremely elevated,whereby the intended photochemical reaction may be promoted sufficientlythroughout the whole thickness of the layer.

The photochemical reaction in the exposed area of the light-sensitivelayer advances by a different mechanism, depending upon the kind of thelight-sensitive composition of the layer. For instance, in the exposedarea of the light-sensitive layer comprising the above-mentionedpositive resist, the high polymer chains in the resin component are cutto give low molecular substances or the insoluble compound is changed toa soluble substance by the photochemical reaction. In the exposed areaof the light-sensitive layer comprising the above-mentioned negativeresist, the high polymer chains in the resin component are crosslinkedto form a two-dimensional or three-dimensional molecular structure.

In the exposed area of the light-sensitive layer of the above-mentionedchemically amplified resist, for example the optical acid oralkali-generating agent generates acid or alkali, and the acid or alkalidecomposes the side chains of the resin component(in the case of apositive resist), or the resin component is crosslinked by acid oralkali catalyzed of crosslinker (in the case of a negative resist).Especially in the case, the patternwise exposed light-sensitive layer isoptionally heat-treated at a temperature falling within the range ofapproximately from 70° C. to 160° C., preferably from 80° C. to 150° C.(post exposure bake, PEB), if desired, so as to promote the amplifyingreaction, i.e., to diffuse the acid as generated in the exposed area ofthe light-sensitive layer as mentioned above so that the reactionbetween the acid or alkali and other components is promoted. The reasonof the definition of the temperature range in the heat treatment step isbecause if the temperature is lower than 70° C., the above-mentionedreaction could not be effected sufficiently, but if it is higher than160° C., the exposed area and the non-exposed area in theradiation-sensitive layer would be decomposed or hardened.

Next in the third step to follow the above-mentioned second step, theabove-mentioned exposed or heat-treated light-sensitive layer isdeveloped with a determined developer. Further, it is rinsed with a purewater to remove the developer and then the substrate is dried.

In the third step (for development), in general, either one of theexposed area and the non-exposed area of the light-sensitive layer isselectively dissolved with the developer and removed to give adetermined pattern. Especially in the present invention, since thephotochemical reaction in the exposed area advances sufficiently, theselectivity between the exposed area and the non-exposed area is high togive a pattern with a high resolving power.

As the developer for the development, usable is an aqueous solution oran aqueous of an organic alkali substance such as tetramethylammoniumhydroxide or of an ordinary inorganic alkali substance, an alcoholsolution or the like. For a resist, the molecular weight of which variesby the photochemical reaction used, and an organic solvent, for example,ketone such as methyl ethyl ketone or methyl isobutyl ketone orcycrohexanone or esters such as butyl acetate or the like may be used asthe developer.

The method of forming a pattern according to an embodiment of thepresent invention is characterized in that a light-sensitive layercontaining an aromatic compound is exposed with light having awavelength range shorter than the maximum wavelength at which maximumabsorption occurs in the third absorption band and longer than awavelength at which maximum absorption occurs in forth absorption band,thereby to cause a photochemical reaction in the light-sensitive layer.

By employing the exposure mode of this kind, the light absorption in thelight-sensitive layer is reduced while the light transmittance throughthe layer is elevated so that the photochemical reaction sufficientlyadvances throughout the whole layer in the direction of the filmthickness. As a result, a pattern having a high resolving power andadditionally having a sufficient dry-etching resistance due to thecharacteristic of the aromatic ring of the above-mentioned aromaticcompound can be obtained.

In the case that a light-sensitive layer containing aromatic compoundincluding an aromatic ring with 3 or less conjugated double bonds, suchas benzene derivatives are used, the exposure with a light having awavelength range shorter than the maximum wavelength at which maximumabsorption occurs in the third absorption band and longer than awavelength at which maximum absorption occurs in forth absorption band,to cause an effective photochemical reaction in the light sensitivelayer.

In the patternwise-exposed step, the light sensitive layer isselectively exposed with a light having a specific wavelength range inaccordance with the composition of the layer to cause a photochemicalreaction in the layer.

In this step, the wavelength range of the exposure light layer issuitably selected in accordance with the above-mentioned definition ofwavelength range depending upon the structure of the aromatic compoundcontained in the layer or upon the structure of the aromatic ring(s) inthe compound. For instance, where the aromatic ring is a benzenering,the wavelength range of the light for exposure is approximatelyfrom 170 to 150 nm, where the ring is a naphthalene ring, it isapproximately from 210 to 170 nm, and where the ring is an anthracenering,it is approximately from 230 to 190 nm. The wavelength range of thelight varies, depending upon the substituent(s) to be introduced intothe aromatic ring. For instance, if a substituent such as a halogen atomor a nitro group is introduced into the ring, the wavelength range ofthe light to be used for exposure is shifted to the long-wavelength sideby about 10 nm or so. Where the substituent has a double bond capable ofbeing conjugated with the double bond of the aromatic ring, it isnoticeably shifted to the long-wavelength side.

The "maximum wavelength in an absorption band" as referred to hereinmeans the peak wavelength in the absorption band(i.e., the wavelengthwith an absorption peak therein). As mentioned above, the absorptionband of an aromatic compound is caused by a light absorption to followthe excitation of the electrons in the aromatic ring of the compound,but it does not contain extremely weak triplet electron transition.Strictly, it is considered that the above-mentioned third absorptionband from the long-wave side is an overlap of two adjacent absorptionsand that it is one in a symmetric molecule.

On the other hands, the compounds including a aromatic ring with from 4to 12 conjugated double bonds in the structure, which are used in themethod of this invention, may generate an relatively strong fluorescentlight by exposure. By using such compounds which generate a fluorescentlight by the exposure, as a light-sensitive layer to form patterns, thelight sensitive layer is exposed by both their radiated light and theinternal fluorescent light generated by irradiation. In particular,since the fluorescent light is generated in the inside of thelight-sensitive layer and it has a longer wavelength range than theirradiated light such as short-wavelength ultraviolet rays or the like,it has excellent light transmittance and/or reactivity in the inside ofthe layer. Therefore, even though the light transmittance of theirradiated light is reduced due to the aromatic rings contained in thelayer, the photochemical reaction may sufficiently advance due to theaction of the fluorescent light with the result that a pattern having ahigh resolving power and an excellent dry-etching resistance can finallybe obtained by the method.

Example of the compound of generating fluorescent light by exposure is aaromatic compound having a structure being destroyed molecularsymmetry.In paticular, the compounds containing aromatic ring(s) withfrom 4 to 12 conjugated double bonds in the structure, which are used inthe second method, may generate an strong fluorescent light by exposure.The compound of generating a fluorescent light and the aromatic compoundcontained in the light-sensitive layer may be the same one. In addition,other various fluorescent dyes may also be used as a compound ofgenerating a fluorescent light by exposure. Various fluorescent dyes maybe added to the above-mentioned aromatic compound so as to elevate theireffect of generating a fluorescent light. Examples of usable fluorescentdyes include acridine orange, aminoacridine, quinacrine,anilinonaphthalene-sulfonic acid derivatives, anthroyloxystearic acid,auramine-O, chlorotetracycline, cyanine dyes such as merocyanine and1,1'-dihexyl-2,2'-oxacarbocyanine, dancyl chloride derivatives such asdansyl sulfoamide, dansyl choline, dansyl galactoside, dansyl tolidineand dansyl chloride, diphenylhexatriene, eosine, ε-adnosine, ethidiumbromide, fluoresceine, formycine,4-benzoylamido-4'-aminostilbene-2,2'-sulfonic acid, β-naphthy1-triphosphoric acid, oxonole dyes, parinaric acid derivatives,perylene, N-phenylnaphthylamine, pyrene, safranine-O, fluorescamine,fluoresceine isocyanate, 7-chloro-4-nitrobenz-2-oxa-1,3-diazole, dancylaziridine, 5-(iodoacetamido-ethyl)aminonaphthalene-1-sulfonic acid,5-iodoacetamido fluoresceine, N-(1-anilinonaphthyl)-4-maleimide,N-(7-dimethyl-4-methylcoumanyl) maleimide, N-(3-pyrene)meleimide, eosine5-iodoacetamide, fluoresceine mercury acete, amino naphthalene compoundssuch as 2- 4'-(2"-iodoacetylamido)amino-naphthalene-6-sulfonic!acid,eosine, and rhodamine derivatives. The amount of the fluorescent dyecontained in the light-sensitive composition (resist) is preferably from1% by weight to 50% by weight of the solid content of the composition.If the amount of the fluorescent dye is less than 1% by weight, theeffect of elevating the sensitivity of the composition is poor, but ifit is more than 50% by weight, the resolving power and the sensitivityof the composition are rather lowered.

In the above-mentioned method, since the light-sensitive layer containsa compound for generating a fluorescent light by which the photochemicalreaction in the layer is promoted, other rays of various wavelengthranges may be used for exposure of the layer. Specific examples ofusable rays include ultraviolet rays, far-ultraviolet rays,vacuum-ultraviolet rays, synchrotron orbital radiation rays,electronrays, X-rays, gamma rays, ion beams, etc.

Next, another method of forming a pattern according to the presentinvention will be explained.

A method practiced according to the present invention comprises;

a step of formimg on a substrate a light sensitive layer comprisinglaminated structure including a first layer including an aromaticcompound and a second layer including a fluorscent light generatingcompound;

a step of patternwise-exposing the light-sensitive layer at least anelectromagnetic radiation to generate a fluorescent light causing photochemical reaction in the first layer at least due to the action of thefluorescent light; and

a step of developing the exposed light-sensitive layer and fluorescentlight-generating layer so as so selectively remove the exposed area ofthe light-sensitive layer.

The compound for generating a fluorescent light by exposure, can bemixed with a suitable resin composition and coated on the substrate as aseparate layer (i.e., as a fluorescent light-generating layer).

In accordance with the method, the photochemical reaction issufficiently promoted in the light-sensitive layer by the action of thefluorescent light to be generated in the fluorescent light-generatinglayer by exposure and also by the action of the irradiated light toresult that a pattern having a high resolving power and having anexcellent dry-etching resistance can finally be obtained.

In the above-mentioned method, for example, inorganic fluorescent agentsmay be used as the compound of including in the fluorescentlight-generating layer. Examples of such fluorescent agents includesalts which are generally used in fluorescent paints, fluorescent lamps,fluorescent bodies for CRT, pigments and others. Specific examples ofthem include MgWO₄, CaWO₄, (Ca,Zn)(PO₄ )₂ :Ti⁺, Ba₂ P₂ O₇ :Ti, BaSi₂ O₅:Pb₂ ⁺, Sr₂ P₂ O₇ :Sn₂ ⁺, SrFB₂ O₃.5 :Eu₂ ⁺, MgAl₁₆ O₂₇ :Eu₂ ⁺,tungstates and the like salts of inorganic acids.

Since the inorganic fluorescent agents generally have poor solubility,they are dispersed in a suitable solvent as a fine powder along with ahigh polymer binder, and the mixing system is coated on a substrate toform a layer. As the binder, any high polymer material in which theabove-mentioned fluorescent agent may be dispersed may be employed. Inconsideration of lamination of the layer along with a light-sensitivelayer on a substrate, the binder is preferably a water-soluble highpolymer. Examples of such high polymer materials include polyvinylalcohol and copolymers of maleic acid, acrylic acid and a vinyl oracrylic compound. The fluorescent agent and the high polymer binder maybe dispersed or dissolved in a solvent, whereupon a surfactant and/or adispersing agent may be added thereto, if desired.

The thickness of the above-mentioned fluorescent light-generating layeris preferably within the range of approximately from 0.05 to 0.5 μm. Ifthe defined range is exceeded, the sensitivity and the resolving powerof the light-sensitive layer is noticeably lowered.

The above-mentioned fluorescent light-generating layer may be formedeither above or below the light-sensitive layer.

Where the layer is formed as an upper layer above the light-sensitivelayer, a mixed system containing the above-mentioned fluorescentlight-generating compound is coated over the light-sensitive layer asformed in the same manner as in the above-mentioned methods, in thethickness as mentioned above. Subsequently, the coated layer is baked ata temperature of approximately from 70 to 120° C. to disperse thesolvent in the mixed system to form the intended fluorescentlight-generating layer. Next, in the same manner as in theabove-mentioned method, the coated base is exposed and then optionallyheat-treated, then the fluorescent light-generating layer is removedwith a suitable solvent or developer, and the exposed light-sensitivelayer is developed to form a pattern.

On the other hand, where the above-mentioned fluorescentlight-generating layer is formed as a lower layer below thelight-sensitive layer, a fluorescent light-generating layer is firstformed on a substrate in the same manner as above. Subsequently, alight-sensitive layer is formed over the layer, and the coated substrateis exposed and then optionally heat-treated and thereafter developed toform a pattern, in the same manner as in the above-mentioned thirdmethod. In this case, the fluorescent light-generating layer formed maybe washed off along with the binder polymer by a spraying method or maybe removed by a dry-etching method. The latter method is especiallypreferred, in which CF₄ or HBr may be used as an etching gas.

By forming the fluorescent light-generating layer as a lower layer belowthe light-sensitive layer in the manner as mentioned above, thephotochemical reaction in the deep range of the light-sensitive layer towhich the irradiating light hardly reaches may well be promoted.

The present invention will be explained in more detail by way of thefollowing examples, which, however, are not intended to restrict thescope of the present invention.

EXAMPLE 1

In the following synthetic Examples 1 and 2, resin compositions to beincorporated into a light-sensitive composition were produced.

Synthetic Example 1

0.3 mol of 2-naphthyl methacrylate and 0.7 mol of tert-butylmethacrylate were mixed with 200 g of toluene, and 2 g ofazoisobutylonitrile (AIBN) was added thereto. The mixed system washeated at a temperature of 70° C. for 8 hours and then purified bydropping it into acetone-methanol solvent, to obtain a copolymer ofnaphthyl methacrylate and tert-butyl methacrylate (Resin A).

The same process as described above was repeated, except that thenaphthyl methacrylate was replaced by vinyl-naphthalene,vinyl-anthracene or vinyl-carbazole, to obtain 3/7 copolymers withtert-butyl methacrylate (Resins D to F).

In addition, a commercial product of β-naphthol novolak (Resin C) wasprepared. The individual resin compositions are mentioned below.

Synthetic Example 2

1-Hydrox-2-naphthylaldehyde was mixed with sodium ethoxide, and ethanolwas removed to obtain sodium salt of 1-hydroxy-2- naphthylaldehyde.Subsequently, benzoyl chloride was dropped to the salt to obtain1-benzoyloxy-2-naphthol-aldehyde. 0.9 mol of malonic acid was added to0.25 mol of 1-benzoyloxy-2-naphthol-aldehyde, and 10 ml of pyridine wasadded thereto and reacted at a temperature of 110° C. for 2 hours toobtain 1-benzoyloxy-2-β-carboxyl)vinylnaphthalene. 0.14 mol of the1-benzoyloxy-2-β-carboxyl)vinylnaphthalene was dissolved in 100 ml ofquinoline, and 5 g of copper powder was added thereto and reacted forfurther one hour at a temperature of 220° C. to obtain1-benzoyloxy-2-vinylnaphthalane. Next, 0.1 mol of1-benzoyloxy-2-vinylnaphthalane was polymerized in benzene in thepresence of AIBN in the same manner as in Synthetic Example 1 to obtainpoly(1-benzoyloxynaphthalene). The poly(1-benzoyloxyvinylnaphthalane) ofan amount corresponding to 0.5 mol of the monomer was dissolved inacetone, and 1 g of aqueous 1N sodium hydroxide solution was addedthereto and heated to obtain poly(vinylnaphthol) (Resin B). The obtainedpolymer was purified by reprecipitating it in an acetone-water-oxalicacid solution.

The compositions of the resins are as follows:

Resin A: 3/7 Copolymer of naphthyl methacrylate and tert-butylmethacrylate (molecular weight: 20,000)

Resin B: poly(vinylnaphthol) (molecular weight: 7,000)

Resin C: β-Naphthol novolak (commercial product, molecular weight :4,500)

Resin D: 3/7 Copolymer of vinylnaphthalene and tert-butyl acrylate(molecular weight: 6,000)

Resin E: 3/7 Copolymer of vinylanthracene and tert-butyl acrylate(molecular weight: 5,500)

Resin F: 3/7 Copolymer of vinylcarbazole and tert-butyl crylate(molecular weight: 7,000)

In addition, the following Resins G to I were prepared. These resinshave no aromatic ring in their structure.

Resin G: poly-tert-butyl acrylate (molecular weight: 12,500)

Resin H: polyallyl methacrylate (molecular weight: 24,000)

Resin I: polyglycidyl methacrylate (molecular weight: 20,000)

In the following synthetic Examples 3 and 4, compounds (dissolutioninhibitors) having bonds capable of being decomposed by an acid, whichare to be incorporated into a light-sensitive composition, wereproduced.

Synthetic Example 3

Polyvinyl naphthol B was reacted with sodium hydride, whereby a part ofthe hydroxyl groups in the polyvinyl naphthol were substituted by sodiumsalts. Subsequently, it was reacted with di-tert-butyl dicarbonate, sothat tert-butoxycarbonyl group was introduced thereinto. Thus,Compound(a) having bonds capable of being decomposed by an acid wasobtained. The proportion of the tert-butoxycarbonyl group introducedinto the compound was 20 mol % of all the hydroxyl groups in thepolyvinylnaphthol.

Synthetic Example 4

Polyvinylnaphthol was reacted with tert-butyl bromoacetate, usingpotassium carbonate and potassium iodide as catalysts, so thattert-butyl acetate was introduced into the polymer. Thus, Compound(d)having bonds capable of being decomposed by an acid was obtained. Theproportion of the tert-butyl acetate as introduced into Compound(b) was19 mol % of all the hydroxyl groups in the polyvinylnaphthol.

In addition, the following compounds having a bond capable of beingdecomposed by an acid were prepared.

Compound(c): Tert-butoxycarbonylnaphthol

Compound(d): Naphthol tert-butyl acetate

Compound(e): Tri-(tert-butoxycarbonyl)anthrarobin

Compound(f): Tert-butoxycarbonyloxyphenanthrene

In the following Synthetic Example 5, an optical acid-generating agentto be incorporated into a light-sensitive composition was produced.

Synthetic Example 5

0.2 mol of anthrarobin was dissolved in tetrahydrofuran, three-molartime of methanesulfonyl chloride was added thereto, and 0.6 mol oftriethylamine was gradually dropped thereinto. Subsequently,triethylamine and tetrahydrofuran were removed from the reaction system,and the product was recrystallized to obtain anthrarobin tri(methanesulfonate) (Compound g).

In addition, the following optical acid generating agents (Compounds hto k)were prepared.

Compound(h): Naphtholnaphthoguinonediazide 4-sulfonate

Compound(i): Triphenylsulfonium trifluorate

Compound(j): Methylsulfonylacetonitrile

Compound(k): Melamine resin (Saimel 325)

Preparation of Light-sensitive Compositions (Resists)

The above-mentioned compounds (components) were combined in accordancewith the formulations as indicated in Table 1 below to preparelight-sensitive compositions 1 to 17. Precisely, ethyl cellosolveacetate was added to the components of the indicated formulation in anamount of three times by weight of the solid contents of the formulationand then stirred for 6 hours at room temperature, and the resultingmixture was filtered through a Teflon filter having a pore diameter of0.2 μm to prepare a varnish of a light-sensitive composition.

                  TABLE 1    ______________________________________    Formulation of Light-Sensitive    Composition (Resist)            Resin     Compound Having Bond                                      Optical Acid    Composition            Component Decomposable With Acid                                      Generating    No.     (Wt. %)   (Wt. %)         Agent (Wt. %)    ______________________________________    1       A(97)     --              i(3)    2       A(95)     --              j(5)    3       B(67), G(30)                      --              i(3)    4       G(50)     a(45)           g(5)    5       G(50)     b(45)           h(5)    6       C(47), G(50)                      --              i(3)    7       D(97)     --              i(3)    8       E(97)     --              i(3)    9       F(97)     --              i(3)    10      G(70)     c(25)           g(5)    11      G(70)     d(30)           i(3)    12      G(65)     e(30)           g(5)    13      G(65)     f(30)           g(5)    14      B(80)     --              i(3), k(17)    15      H(47), B(50)                      --              i(3)    16      I(47), B(50)                      --              i(3)    17      B(70), G(20)                      --              h(10)    ______________________________________

Using the above-mentioned light-sensitive compositions, patterns wereformed.

Each varnish of the light-sensitive compositions Nos. 1 to 17 as shownin Table 1 above was coated on a 5-inch silicon wafer by spin-coatingand then pre-baked on a hot plate of 110° C. for 5 minutes to form alight-sensitive layer (resist film) having a thickness of 0.9 μm.

Next, the light-sensitive layer was patternwise-exposed to an ArFexcimer laser ray (having a wavelength of 193 nm) by contact-exposureand then baked on a hot plate of 110° C. for 2 minutes. Subsequently,the wafer was dipped in the developer shown in Table 2 below for 60 to200 seconds to develop the light-sensitive layer. Further, thethus-developed wafer was washed with water and dried to form a patterncomposed of determined lines and spaces.

The thus-formed patterns were observed with scanning electromicroscope(hereinafter referred to as SEM) to evaluate the resolution of them.With respect to the patterns thus-formed, the data of the sensitivityand the resolution (width of lines of pattern)of the light-sensitivelayer (formed of the light-sensitive composition) are shown in Table 2below.

                  TABLE 2    ______________________________________    Formation of Patterns (Example 1)    Composition             Sensitivity                       Resolution    No.      (mJ/cm.sup.2)                       (μm)    Developer    ______________________________________    1        120       0.4(positive)                                  2.38% TMAH    2        200       0.4(positive)                                  2.38% TMAH    3        95        0.4(positive)                                  2.38% TMAH    4        115       0.4(positive)                                  2.38% TMAH    5        140       0.4(positive)                                  2.38% TMAH    6        240       0.4(positive)                                  2.38% TMAH    7        180       0.4(positive)                                  2.38% TMAH    8        210       0.4(positive)                                  2.38% TMAH    9        220       0.5(positive)                                  2.38% TMAH    10       120       0.4(positive)                                  2.38% TMAH    11       140       0.4(positive)                                  2.38% TMAH    12       160       0.5(positive)                                  2.38% TMAH    13       160       0.5(positive)                                  2.38% TMAH    14       75        0.5(negative)                                  2.38% TMAH    15       80        0.5(negative)                                  Ethanol 2.38% TMAH    16       90        0.5(negative)                                  Ethanol 2.38% TMAH    17       150       0.5(positive)                                  2.38% TMAH    ______________________________________     Condition: Contactexposure with ArF excimer laser ray postexposure bakin     at 110° C. for 2 minutes     Thickness of lightsensitive layer: 0.9 μm     Developer: TMAH(2.38% water solution of tetramethylammonium hydroxide)

EXAMPLE 2

The polymer components, which were incorporated into the light sensitivecompositions, were synthesized with following method.

A commercial product of acetal resin (Esreck BLS manufactured by SEKISUICHEMICAL Co., Ltd) (resin J) was prepared.

In the following synthetic Examples 6 and 7, acetal resins withfunctional groups were synthesized by using following method.

Synthetic Example 6

2 g of polyvinyl alcohol(molecular weight: 22500), 3 ml of glyoxylicacid, and 4.5 ml of concentrated H₂ SO₄ were dissolved in 30 ml ofwater, The solution was heated at 60° C. for 48 hours, then it wasneutralized to obtained glyoxylicacidsubstituted acetal polymer ofpolyvinyl alcohol(resin K). 20 mol % of acetal substituted-OH in PVP.The obtained polymer and reprecipitated by using water-methanolsolution.

Synthetic Example 7

Amono-acetal substituted polymer of polyvinyl alcohole (resin L) wasobtained by a method described in a references(Colloid Polym Sci.252,294(1974)). 5 mol % of amino acetal substituted-OH.

Using the methods in the following synthetic Examples 8 and 9, epoxyresin compositions for incorporation into a light-sensitive compositionwere prepared.

Synthetic Example 8

0.05 mol of 1,5-naphthalenediol was mixed with 0.1 mol ofepichlorohydrine, then gradually added 0.25 g of water, and 4.0 g ofNaOH. The mixture system was heated at 70° C. for 2 hours and thenunreactant epichlorohydrine, was removed under the reduced pressure at30 mm Hg, then epoxy resin was extracted with toluene.

After removing toluene under the reduced pressure, epoxy resin of1,5-naphthalenediol (resin M) was obtained.

Synthetic Example 9

0.05 mol of 4,4"-methlenebis(dihydroxy naphthalene) was mixed with 0.1mol of epichlorohydrine, then added 0.25 g of water, and 0.8 g of NaOH.The mixture was heated at 70° C. for 2 hours then, unreactantepichlorohydrine was removed under reduced pressure at 30 mm Hg then,epoxy resin was extracted with toluene.

After removing the toluene under reduced pressure, partially epoxy groupintroduced 4,4"-methlenebis(dihydroxy naphthalene)(resin N) wasobtained.

Synthetic Example 10

0.3 mol of trimethyl sililmethacrylate and 0.7 mol ofgricidylmethacrylate was mixed with g of toluene. Then,azoisobuthylnitoril was added and heated at 70° C. for 8 hours. Theproduct was prepicitated dropwise to acetone-methanol solution to obtain3/7 copoylmer of trimethylsililmethacrylate and gricidyl methacrylate(molecular weight: 10000)

After stirring the products in an acetone-acidic acid-water mixedsolution for one hour to remove trimethylsilyl group protecting, andreprecipitating it in water. After these treatments, the 3/7 copolymerof methacrylic acid and gricidyl methacrylate (resin O) was obtained.

In addition, a commercial products resin P: epoxy resin of1,6-naphthalenediol (manufactured by DAINIHON INK Co., Ltd), resin Q :epoxy resin of 4,4"-methylenebis(dihydroxylnaphthalene) (manufactured byDAINIHON INK Co., Ltd)

resin R: epoxy resin of4,4-methylene-bis(dihydroxylnaphthalene)(manufactured by Aldric Co.)

resin S: cycro aliphatic epoxy resin (CY179 manufactured by Ciba GeigyLtd.)

The following acid or alkali generating agent to be incorporated into alight-sensitive composition(l), (m), and (n). were prepared.compound(l): triphenylsulfonium trifluorate(manufactured by MIDORI Co.,LTD)

compound(m):2-(4-methoxynapftyl)-4,6-bis(trichloromethyl)-1,3,5-triazine.(manufactured by MIDORI Co., LTD)

compound(n):nitrobenzylcycrohehxyl carbamate(manufactured by MIDORI Co.,LTD)

With respect to preparation of light sensitive compositions(resists) theabove-mentioned compounds were combined in accordance with theformulations as indicated in table 3 below to prepare light sensitivecompositions 18 to 24. Precisely, ethyl cellosolve acetate was added tothe components of the indicated formulation, in an amount of three timesby weight of the solid content of the formulation and then stirred for 6hours at room temperature, and the resulting mixture was filteredthrough a Teflon filter having a pore diameter of 0.2 μm to prepare avarnish of a light-sensitive composition.

                  TABLE 3    ______________________________________    Formulation of light sensitive composition(resist)                                      Optical Acid                                      or Alkali    Composition            Acetal Resin Epoxy Resin  Generating    No.     Component(Wt. %)                         Component(Wt. %)                                      Agent(Wt. %)    ______________________________________    18      J(73)        M(25)        l(2)    19      K(75)        N(25)        l(1)    20      K(75)        N(20)        m(5)    21      K(75)        N(20)        n(5)    22      L(78)        P(20)        l(2)    23      K(49)        S(20), Q(30) l(2)    24      O(74)        R(25)        l(1)    ______________________________________

Using the above-listed light-sensitive compositions, patterns wereformed.

Each varnish of the light sensitive compositions Nos. 18 to 24 as shownin Table 3 above was coated on a 5-inch silicon wafer by spin-coatingand then pre-baked on a hot plate at 110° C. for 5 minutes to form alight-sensitive layer (resist layer) having a thickness of 0.9 μm.

Next, the light-sensitive layer was patternwise-exposed to an ArFexcimer laser ray (having a wavelength of 193 nm) by contact-exposure,and then baked on a hot plate of 110° C. for 2 minutes, subsequently,the wafer was dipped in the developer shown in Table 4 for 60 to 200seconds to develop the light sensitive layer.

Further, the thus-developed wafer was washed with after and dried toform a desired patterns with lines and spaces.

Thus-faleicated patterns were observed with SEM to evaluate theresolution of them. The data of the sensitivity and theresolution(minimum width of lines which can be resolved) of thelight-sensitive layer (formed with the light-sensitive composition) areshown in Table 4 with respect to the obtained patterns.

                  TABLE 4    ______________________________________    Formulation of Patterns (Example 2)    Composition              Sensitivity  Resolution    No.       (mJ/cm.sup.2)                           (μm)  Developer    ______________________________________    18        15           0.5      MIBK    19        25           0.5      3.0% TMAH    20        80           0.5      3.0% TMAH    21        75           1.0      3.0% TMAH    22        20           0.5      MIBK    23        10           0.5      MIBK    24        30           0.5      3.0% TMAH    ______________________________________     Condition: Contactexposure with ArF excimer laser ray Postexposure baking     at 110° C. for 2 minutes     Thickness of lightsensitive layer: 0.9 m     Developer: TMAH(tetramathylammonium hydroxide) solution of the water     MIBK (methylisobuthylketone)

Next, an absorbance at 193 nm of the light-sensitive layer (formed ofthe light-sensitive composition 18-24) having 1 μm thick were measured.

The data of the absorbance of the light-sensitive layer (formed with thelight-sensitive composition) are shown in Table 5. On the other hand, anabsorbance at 193 nm of the light-sensitive layer formed of thecommercial photoresist OFPR-800 (Manufactured TOKYO OHKA Co., Ltd)having 1 μm thick were also measured as a comparative example. The dataof the absorbance of the light-sensitive layer (formed with thelight-sensitive composition) are shown in Table 5.

Using the pattern formed from light-sensitive compositions 18-24 andOFPR-800 as an etching-resistant mask, etching rates for reactive ionetching using CF₄ , plasma (50 mTorr, 80 W) were measured. The data ofthe etching rate of the light-sensitive layer (formed of thelight-sensitive composition 18-24 and OFPR-800) are shown in Table 5

Using the pattern formed from light-sensitive compositions No. 18-24 andOFPR-800 as an etching resistmasku, etching Using CF₄, plasma(50 m Torr,80 W) were measured. The data of the etcing rate of the light sensitivelayer (formed of the light-sensitive composition No. 18-24 and OFPR-800)are shown TABLE-5

                  TABLE 5    ______________________________________                              Etching rate    Composition No. Ansorbance                              (nm/min)    ______________________________________    18              0.6       3.1    19              0.5       3.0    20              0.5       3.5    21              0.7       3.0    22              0.6       3.2    23              0.5       3.5    24              0.5       3.0    OFPR-800        30.0      3.0    ______________________________________

From the results, it is obvious that the pattern as formed in theexamples of the present invention have very high tranceparency to ArFexcimer laser compared relatively with OFPR-800, and also have enoughhigh dry etching resistance, which are almost same as that for OFPR-800,enabling conventional LSI fabrications.

EXAMPLE 3

To the varnish of light-sensitive composition No.17 was added pyrene(compound of generating a fluorescent light) in an amount of 3% byweight of the solid content of the varnish, and the resulting mixturewas again filtered to give light-sensitive composition No. 25. UsingComposition No.25, a pattern was formed in accordance with the samemethod and condition as in Example 1. As a developer, an aqueous 2.38%tetramethylammonium hydroxide solution was used.

Table 6 below shows the sensitivity and resolution of thelight-sensitive layer Example 3 as well as the shape of the crosssection of the pattern formed therein. It also shows the sensitivity andresolution(width of lines of pattern) of the light-sensitive layer madefrom Light-sensitive Composition No. 17 of Example 1 along with theshape of the cross section of the pattern formed therein.

EXAMPLE 4

5% by weight of MgWO₄ powder (compound for generating a fluorescentlight) and polyvinyl acrylate were mixed in water, and 1% of asurfactant. Epikote was added thereto.

The resulting dispersion was coated on a substrate and heated at 200° C.for 5 minutes to form a thin film of a fluorescent light-generatinglayer having a thickness of 0.1 μm on the substrate. A varnish oflight-sensitive composition No.17 was coated over the layer byspin-coating. The thus-coated substrate was then exposed and developedin accordance with the same method and condition as in Example 1 to forma pattern thereon. As a developer, an aqueous 2.38% tetramethylammoniumhydroxide solution was used.

The present example corresponds above described to the fourth methodaccording to the present invention.

The sensitivity and resolution(width of lines of pattern) of thelight-sensitive layer of the present example and also the shape of thecross section of the pattern formed therein are shown in Table 6 below.

                  TABLE 6    ______________________________________    Formation of Patterns    Test  Sensitivity                     Resolution                               Shape of Cross Section    No.   (mJ/cm.sup.2)                     (μm)   of Pattern    ______________________________________    *1    150        0.5                               1 #STR4##    *2    120        0.4                               2 #STR5##    *3    120        0.4                               3 #STR6##    ______________________________________     *Test 1: The pattern was formed using lightsensitive composition No.17.     *Test 2: The pattern was formed using lightsensitive composition No.24     (containing a compound of generating a fluorescent light).     *Test 3: The pattern was formed using lightsensitive composition No.17 as     coated over the fluorescent lightgenerating layer formed on the substrate

EXAMPLE 5

A light-sensitive layer was formed on a substrate, using Light-sensitivecomposition No. 17. Over the layer, the same dispersion of thefluorescent light-generating compound as used in Example 3 was coatedand heated at a temperature of 200° C. for 5 minutes to form a thin filmof a fluorescent light-generating layer having a thickness of 0.1 μmSubsequently, the light-sensitive layer and the fluorescentlight-generating layer were exposed to electron beams of 20 keV and thendeveloped in accordance with the same method and condition as in Example1 to form a pattern on the substrate.

In the present example, the sensitivity of the light-sensitive layer was5 μC/cm² to form a pattern having a line width of 0.3 μm.

For comparison, where the light-sensitive layer was directly formed onthe base without forming the fluorescent light-generating layer thereon,no pattern was formed.

Comparative Example

A comparative light-sensitive composition No. 26 was prepared in thesame manner as in preparation of light-sensitive composition No. 3,except that Resin B in the resin composition was replaced bypolyvinylphenol (having a molecular weight of 6,000).

Using Composition No. 26, a pattern was formed by exposure with an ArFexcimer laser in accordance with the same method and condition as inExample 1. However, a satisfactory pattern could not be formed even byexposure of 500 mJ.

Referential Example

Using the pattern formed from light-sensitive composition No. 3 inExample 1 as an etching-resistant mask, active ion etching was effectedwith CF₄ plasma, whereupon the etching rate was 47 mm/min.

For comparison, a pattern was formed on a substrate, using a resist ofpolymethyl methacrylate (PUMA) in accordance with the same method andcondition as in Example 1. Using the pattern thus-formed as anetching-resistant mask, active ion etching was also effected in the samemanner as described above, whereupon the etching rate was 140 mm/min.

From the results, it is obvious that the patterns as formed in theexamples of the present invention have a higher dry-etching resistanceby about three times or more than the pattern formed from PUMA by ArFexcimer laser exposure.

As explained in detail above, the present invention provides methods offorming patterns by short-wavelength light exposure. In accordance withthe methods of the present invention, patterns having a high resolvingpower and an excellent dry-etching resistance are formed stably. Themethods of the present invention can be applied effectively tolithography in the process of producing semiconductor devices and haveexcellent values in the industrial field.

While the invention has been description detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modification can be made therein withoutdeparting from the spirit and scope thereof.

What we claim is:
 1. A method of forming a pattern on a substratecomprising the steps of:depositing on said substrate a light-sensitivelayer comprising an aromatic compound containing an aromatic ring having4 to 12 double bonds in conjugation; patternwise exposing saidlight-sensitive layer to electromagnetic radiation having a wavelengthof from 180 to 220 nm so as to cause a photochemical reaction in saidlight-sensitive layer; and developing the exposed light-sensitive layer,wherein the proportion of aromatic rings containing 4 to 12 double bondsin conjugation in said light-sensitive layer is about 75% to 100% byweight based on the total weight of aromatic rings therein.
 2. Themethod of claim 1, wherein said radiation has a wavelength of less than200 nm.
 3. The method of forming a pattern as claimed in claim 1,wherein the light-sensitive layer comprises copolymer including naphthylmethacrylate.
 4. The method of forming a pattern as claimed in claim 1,wherein the light-sensitive layer comprises a copolymer comprisingpolymerized vinylnaphthalene monomers.
 5. The method of claim 1, whereinsaid aromatic compound contains a benzene ring or a pyridine ring. 6.The method of claim 1, wherein said aromatic compound contains a singlemonocyclic ring.
 7. The method of claim 1, wherein said aromaticcompound contains a polycyclic compound consisting of 6-membered rings.8. The method of claim 7, wherein said polycyclic compound is selectedfrom the group consisting of naphthalene, anthracene and phenanthrene.9. The method of forming a pattern as claimed in claim 1, wherein thelight-sensitive layer is composed of a composition which comprises:(a)acetal resin having a unit represented by following formulas (1) and atleast one unit selected from units represented by following formulas(2), (3) and (4): ##STR7## (wherein R₆ represents alkyl group, R₇represents carboxylic group or alkyl group with an amino group, R₈represents an aromatic group, l, m, n≧0,l+m+n>0, x>0) (b) epoxy compoundincluding in the skeleton a naphthalene ring,and (c) a compound capableof generating an acid or alkali by exposure.
 10. The method of forming apattern as claimed in claim 1, wherein the light sensitive compositioncomprises:a copolymer of vinyl compounds having an epoxy group in theside chain, a polyhydroxide compound having naphtalene ring in theskeleton, and a compound capable of generating an acid or alkaki byexposure.
 11. The method of forming a pattern as claimed in claim 1,wherein the light-sensitive layer comprises naphthoquinonediazidesulfonate ester of naphthol or2-(4-methoxynaphthul)4,6-bis(trichlorometyl)-1,3,5-triazine as anoptical acid generating agent.
 12. A method of forming a pattern on asubstrate comprising the steps of:depositing on said substrate alight-sensitive layer comprising an aromatic compound containing anaromatic ring having 4 to 12 double bonds in conjugation; patternwiseexposing said light-sensitive layer to electromagnetic radiation havinga wavelength of from 180 to 220 nm so as to cause a photochemicalreaction in said light-sensitive layer; and developing the exposedlight-sensitive layer, wherein the proportion of aromatic ringscontaining 4 to 12 double bonds in conjugation in said light-sensitivelayer is about 75% to 100% by weight based on the total weight ofaromatic rings therein, wherein said aromatic compound is substituted bya hydroxyl group or a protected hydroxyl group of the formula --OR₅,where R₅ represents tert-butyl or tert-butoxycarbonyl.
 13. The method ofclaim 12, wherein said aromatic compound contains a polycyclic compoundconsisting of 6-membered rings.
 14. The method of claim 13, wherein saidpolycyclic compound is selected from the group consisting ofnaphthalene, anthracene and phenanthrene.
 15. A method of forming apattern on a substrate comprising the steps of:depositing on saidsubstrate a light-sensitive layer comprising an aromatic compoundcontaining an aromatic ring having 4 to 12 double bonds in conjugation;patternwise exposing said light-sensitive layer to electromagneticradiation having a wavelength of from 180 to 220 nm so as to cause aphotochemical reaction in said light-sensitive layer; and developing theexposed light-sensitive layer, wherein the proportion of aromatic ringscontaining 4 to 12 double bonds in conjugation in said light-sensitivelayer is about 75% to 100% by weight based on the total weight ofaromatic rings therein, wherein the aromatic compound ispoly(vinylnaphthol) or a copolymer comprising polymerized vinylnaphtholmonomers.
 16. A method of forming a pattern on a substrate comprisingthe steps of:depositing on said substrate a light-sensitive layercomprising an aromatic compound containing an aromatic ring having 4 to12 double bonds in conjugation; patternwise exposing saidlight-sensitive layer to electromagnetic radiation having a wavelengthof from 180 to 220 nm so as to cause a photochemical reaction in saidlight-sensitive layer; and developing the exposed light-sensitive layer,wherein the proportion of aromatic rings containing 4 to 12 double bondsin conjugation in said light-sensitive layer is about 75% to 100% byweight based on the total weight of aromatic rings therein, whereinelectromagnetic radiation is generated from an ArF excimer laser or afifth harmonic of YAG laser.
 17. The method of claim 16, wherein saidaromatic compound contains a polycyclic compound consisting of6-membered rings.
 18. The method of claim 17, wherein said polycycliccompound is selected from the group consisting of naphthalene,anthracene and phenanthrene.
 19. A method of forming a pattern on asubstrate comprising the steps of:depositing on said substrate alight-sensitive layer comprising an aromatic compound containing anaromatic ring having 4 to 12 double bonds in conjugation; patternwiseexposing said light-sensitive layer to electromagnetic radiation havinga wavelength of from 180 to 220 nm so as to cause a photochemicalreaction in said light-sensitive layer; and developing the exposedlight-sensitive layer; wherein the proportion of aromatic ringscontaining 4 to 12 double bonds in conjugation in said light-sensitivelayer is about 75% to 100% by weight based on the total weight ofaromatic rings therein, wherein said radiation has a wavelength of about193 nm.
 20. The method of claim 19, wherein said aromatic compoundcontains a polycyclic compound consisting of 6-membered rings.
 21. Themethod of claim 20, wherein said polycyclic compound is selected fromthe group consisting of naphthaiene, anthracene and phenanthrene.